In order to function properly, the human eye must be constantly cleaned and bathed with a saline solution to eliminate dirt, dust or other irritants from the surface of the eye. Most humans have this saline solution automatically introduced to the eye by means of a tear duct. This duct is activated by the blinking action of the eye which in turn is actuated by the brain sensing certain irritants on the surface of the eye. Unfortunately, many people are incapable of producing their own tears and therefore this saline solution must be introduced to the eye by other means.
The prior art shows that several systems such as a gravity feed system and a mobile infusion system have been developed for dealing with this problem. While these systems do introduce artificial tears to the eye, they are not without their drawbacks. The gravity feed system is described by Flynn and Schulmeister in "Keratoconjunctivitis Sicca and New Techniques in its Management", Medical Journal of Australia, 1:34, 1967. In this system, artificial tears are supplied to the eye from a reservoir attached to the frame of a pair of eyeglasses. With the aid of gravity, the fluid flows from the reservoir through a series of tubes and into the inner corner of the eye. The main fault of this system, which the present invention overcomes, is the lack of control in the gravity feed system. When the patient's head position changes (i.e. when he is looking up or down), the flow rate of this gravity feed system automatically changes. Furthermore, the gravity feed system does not have an easily controlled and reliable adjustment for changes in atmospheric condition.
One mobile infusion system has been described by Dohlman, Doane and Reshni in "Mobile Infusion Pumps for Continuous Delivery of Fluid and Therapeutic Agents to the Eye" which was published in Annals of Ophthal., February, 126, 1971. This paper describes a battery powered device which is worn on the body to pump the artificial tear solution to the eye. However, this device weighs approximately 25 ounces and therefore cannot be conveniently mounted on the frame of a pair of eyeglasses. Additionally, this infusion pump has a high initial cost and some operating cost due to component replacement and battery recharge. In addition, the rate of flow of this mobile infusion system can only be adjusted by removing the infusion pump from the body and adjusting it with the use of a flow meter.
A second mobile infusion system is described in "A New Extracorporeal Tear Duct", published in the Proceedings of A.C.E.M.B., 13:275, 1971, authored by Summers and Doane. This paper reports on a battery powered device, approximately the size of a cigarette pack, for pumping the solution to the eye. The main problems of this device are vibration and wear. This pump, which is a solenoid driven plunger pump, vibrates excessively and some of its parts have a very high wear rate.
A third mobile infusion pump has been developed by Sage Instruments, Inc. of White Plains, N.Y. This Sage Microflow Pump Model 216 operates by displacing the artificial tears contained in a reservoir with a gas which is generated from an electrolytic gel. The main problems with this pump are unreliability, high operating cost, and difficulty of operation. Patients have complained that the pump stops frequently and does not easily start. Also, cost of replacing the gel is high in addition to the operation being very untidy.
U.S. patents to Ness (U.S. Pat. Nos. 3,416,530 and 3,618,604) and to Neefe (U.S. Pat. Nos. 3,710,796 and 3,786,812) all show different ocular inserts for delivering drugs to the eye. However, none of these inserts are activated by the blinking motion of the patient's eye.